1. Field of the Invention
The present invention relates generally to electrical signal connectors and more particularly to a connector terminal, which comprises a metal socket having a metal coating layer coated on inner and outer surface thereof, a probe head, an elastic member floatably supporting the probe head partially in the metal socket and a plug plugged into a bottom through hole of the metal socket, and which has the characteristic of low resistivity (high conductivity) and high level of signal transmission efficiency and stability.
2. Description of the Related Art
With the rapid development of electronic technology and multimedia revolution, cell phone, smart phone, GPS navigation device, PDA and many other mobile electronics are created and widely used in different fields. It is now the market tendency to create mobile devices having light, thin, short and small characteristics. In consequence, electronic components for installation in a circuit board for mobile device must be made smaller, more precise and stronger than ever before.
Further electrical connectors are intensively used to connect electronic devices to a circuit board. An electrical connector generally comprises a plurality of signal connector terminals and power connector terminals connected with respective conductors of a cable for transmitting signal or power supply to a control circuit. As electrical connectors get ever smaller, many new types of electrical connectors are created. For example, a pogo pin connector is a spring loaded connector used in an electronic device to establish a connection between two printed circuit boards. A pogo pin generally comprises a metal socket (cylinder), a probe head mounted in the metal socket, and a spring mounted inside the metal socket to support the probe head. When the probe head is forced toward the inside of the metal socket by an external pressure, the spring can be elastically deformed. Subject to contact between the probe head and the inside wall of the metal socket, the pogo pin achieves electrical connection between two printed circuit boards. For the advantages of small size, large current, strong contact point, high durability and connection stability, pogo pin connectors are widely used in cell phone battery, antenna connectors, GPS navigation device, tablet computer, handheld computer, wireless receiver or wireless communication device for conducting electric current or transmitting signals.
Further, when the probe head of a pogo pin is forced toward the inside of the metal socket to compress the spring, the elastic potential energy of the spring forces the probe head to stop against a part of the inside wall of the metal socket, achieving electric connection. To ensure connection stability, the inner and outer surface of a metal socket for pogo pin will be electroplated with a metal coating layer to enhance conductivity and to provide a better bonding surface. During electroplating, metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material.
However, as the metal socket of a pogo pin is a blind hole structure, gases (hydrogen and etc.) released during electroplating may be accumulated in the blind hole of the metal socket, causing cracks in the metal coating layer, or affecting even distribution of electric current to lower the speed of the deposition of metal ions on the surface of the metal socket. Due to low current efficiency (the ratio of the amount of electricity, in coulombs, theoretically required to yield a given quantity of material in an electrochemical process, to the amount actually consumed), it takes much plating time to reach the desired coating thickness. Because of slow deposition rate, it is difficult to coat the desired metal coating layer on the inner surface of the metal socket. In consequence, the manufacturing cost of the metal socket is high.